The Volcano Devils – photographer and filmmakers Maurice and Katia Krafft – were individuals independent of faculty association and government funding. They were professionals passionate about documenting volcano activity, offering precious images that volcanologists around the world use as reference. In about twenty-three years of work, they witnessed 120 volcanic eruptions and filmed approximately 500 hours of footage.

The “Volcano Devils” are credited for capturing the only images available of a pyroclastic flow, one of the most dangerous phenomenons around volcanic activities. This type of fast-moving flow is a blend of gas and particles (like ash, lava and rock). Pyroclastic flow is heavier than air and can reach temperatures of up to 1,500 degrees Fahrenheit and travel speeds of 150 miles per hour.

When a volcano has an explosive eruption (or when the dome top collapses), these pyroclastic flows move down the sides of the volcano, generally following valleys. And due to their speed, composition and temperature, pyroclastic flows have the potential to demolish cities and wipe out its inhabitants – like the 1902 eruption of Mount Pelée, which killed about 30,000 people and incinerated a whole city.

Maurice and Katia Kraff perished in the spring of 1991 while filming the eruption of Mount Unzen. Discover more about their work as the “Volcano Devils” and find out what happened during their last expedition…

Watch Man versus Volcano on Thursday, April 7th at 10 PM et/pt on the National Geographic Channel!